In modern semiconductor devices, there is often a need to monitor the temperature of a device during operation. Temperature monitoring may be useful in a wide variety of circumstances. For example, it may be useful to cease or modify operations associated with a semiconductor device when excessive heat buildup is detected because rising temperatures may lead to reduced performance or even damage to the semiconductor device. Additionally, the monitored temperature may be used to control the operation of cooling devices, such as fans or refrigeration devices.
Alternatively, in some applications, the semiconductor device may be designed to operate within a preselected temperature range and thus heating or cooling may be required. To maintain operation of the device at a target temperature it may be useful to monitor the temperature and then increase/decrease heating or cooling, as needed, to maintain the desired operating temperature. In other applications, the operating characteristics of the semiconductor device may change with increasing temperatures. Therefore, it may be useful to monitor the temperature of the device and accommodate its operating characteristics at a particular temperature.
Conventional temperature sensors have a variety of shortcomings. For example, conventional temperature sensors consume excessive power. Power consumption is a significant factor in electronic devices. It is desirable to reduce power consumption when implementing certain applications. In particular, wireless and battery operated equipment require lower power consumption designs to operate for acceptably long periods of time.
Conventional temperature sensors are also known to produce significant heat, contributing to the heating issues discussed above. Temperature sensors hat produce significant heat are difficult to incorporate within a common substrate with a semiconductor device, such as semiconductor memory, microprocessors, digital signal processors, and the like. Temperature sensors that are formed in a separate semiconductor device are expensive and prone to performance variations that arise from differences in manufacturing parameters. Furthermore, other conventional temperature sensors that use P-N junction parameters, while highly sensitive to temperature change, are sensitive to process deviations and may require extensive calibration of each individual die for proper operation.
Also, there is a drive within the electronics industry to design smaller and more efficient electronic circuitry for many devices, such as cameras, personal digital assistants (PDAs), wireless telephones, cellular phones, portable computers, portable sensors and a variety of small, hand-held electronic equipment. Conventional temperature sensors tend to be relatively large devices that consume substantial semiconductor real estate. The size of these temperature sensors renders their incorporation into a common substrate with the semiconductor device impractical.
As a result, there is a need for a compact temperature sensor that can be readily incorporated into the structure of a semiconductor die and provide an absolute temperature for use in modifying the performance of temperature sensitive circuitry.